In the fabrication of electronic assemblies, semiconductor dice are sometimes wire bonded to substrates. For example, multi chip modules, such as memory modules (e.g., SIMMs, DIMMs), can include multiple bare dice wire bonded to a substrate. Typically, the substrates comprise an electrically insulating material, such as ceramic or FR-4. The substrates can also include conductors (e.g., metal traces) which electrically interconnect the dice.
The wire bonds electrically connect bond pads on the dice to corresponding bond pads on the conductors. With some assemblies, the dice and wire bonds are subsequently encapsulated in a plastic resin. Repair sites are also sometimes included on the substrates for mounting replacement dice for defective dice.
With this type of electronic assembly, the substrates can also include edge connectors in electrical communication with the conductors on the substrate. The edge connectors allow electrical paths to be made from the outside to the dice. For example, an edge connector on a substrate can be configured for electrical engagement with a mating electrical connector of a computer or other electronic device.
In order to test the electrical characteristics of an electronic assembly, and the dice contained on the assembly, standard tests can be performed. In the past, these tests have been performed on the completed assembly by applying test signals through the substrate edge connectors. For example, tests can be used to identify electrical defects in the assembly such as opens, shorts and high resistance.
The dice on the assembly can also be functionally tested to evaluate their individual electrical characteristics, and to evaluate the electrical characteristics of the assembly as a whole. For functionally testing the dice, test signals can be written to selected address and input/output ports for the assembly. The resultant signals can then be read to determine if the read data matches predetermined parameters. Substandard or defective dice can then be identified and replaced as required.
One shortcoming of this approach is that the defects are detected only after the assembly has been completed, and the dice and wire bonds have been encapsulated. It would be advantageous to provide a test procedure in which defects can be identified prior to completion of the assembly. This would permit defective components to be identified prior to incurring the time and expense of completing the assemblies.
The present invention is directed to a method and system for fabricating and testing electronic assemblies that include semiconductor dice wire bonded to substrates. The method includes testing prior to completion of the assembly, so that defective components can be identified early in the manufacturing process, before full manufacturing expenses are incurred.